The specific aim of this follow-up study is to assess the significance of previously reported factors determining neuropsychological development of higher language, verbal and non-verbal cognitive functions and lower sensory and motor functions in a 6 year follow-up study of 295 children and young adults with hydrocephalus and in 149 normal control children. In view of the current lack of any longitudinal neuropsychological follow-up studies of hydrocephalics, this study will provide unique opportunities to investigate the dynamics of cerebral development and outcome in hydrocephalus. The findings of this study will have conceivably important practical implications for future assessment and treatment of hydrocephalics, and other children and young adults with diffuse brain insults. Finally, the findings of this study will provide bases for further elucidation of principles underlying organization, disorganization and reorganization of human brain function.